By: Samantha Page, Climate Reporter, ThinkProgress

The District Court of Appeals for the D.C. Circuit will hear arguments Tuesday at a special, 9-judge hearing over the legality of the EPA’s Clean Power Plan. The plan is currently on hold, after the Supreme Court granted a stay of implementation while the courts have their say.

Here’s the short version: Some people think the EPA doesn’t have the authority to limit carbon emissions from power plants, because the agency already limits other pollutants from power plants. Others think that argument is hogwash — and that limiting carbon is pretty important. (Reminder: greenhouse gas emissions, such as carbon dioxide, are driving anthropogenic climate change that threatens our cities, health, water, and very way of life.)

So as attorneys on both sides prep for Tuesday’s Clean Power Plan arguments, it’s a good time to take a look at what the plan actually is, what it could do, and why it has embroiled nearly all the states in legal action.

1. What is it?

We’ve been over this before, but for those of you who need a refresher, the Clean Power Plan is a federal (EPA) mandate for states to curb carbon emissions from their electricity providers. Electricity — largely from burning coal — produces nearly a third of the United States’ greenhouse gas emissions. Until very recently, electricity was the largest contributor the nation’s carbon footprint, but it has recently been unseated by transportation. (Thanks, low oil prices.) Under the CPP, each state has to figure out how to get a mix of clean and lower-carbon electricity sources online, submit their plan to the EPA, and achieve carbon emissions reductions.

2. What is it not?

It is not a job-killing proposal from Big Government to strip hard-working Americans of their cheap energy.

3. Is it important?

Yes.

This is arguably the single most important piece of climate action the Obama administration has taken. And that’s saying a lot. The CPP is one of the only national plans that will help us achieve our carbon emissions reduction goals and help prevent 2 degrees Celsius of global warming.

4. Is it doable?

Yep.

In fact, most states are already on track to hit their targets. An article from the normally staid Reuters this week was headlined, “Most states on track to meet emissions targets they call burden.” And some of these states, such as North Carolina, have experienced a boom in clean energy jobs and have benefited from companies moving in that want to source their electricity from green generation.

5. What’s the problem, then?

Climate deniers.

Coal interests.

Money.

A lot of politicians are making this about coal communities. But, frankly, coal communities have been getting the short end of the stick for a long time. After being told for generations that they were making a sacrifice to keep the lights on and America running (they were), these people now aren’t getting compensated for that sacrifice. Coal companies — and coal executives, specifically — have acted atrociously, backtracking on commitments to keep up pension plans, paying themselves massive bonuses while declaring bankruptcy, and continuing to donate to politicians who refuse to hold coal accountable for destroying both the environment and the health of the people who worked for them.

When people are told they might lose their jobs, it hurts. But in the long-term, for the country, the CPP will actually bring more economic benefit than pain, according to the non-partisan think tank Economic Policy Institute, which found that the CPP would lead to nearly 100,000 more U.S. jobs by 2020 than the business-as-usual scenario.

6. That sounds pretty good. Are there other benefits, beyond a livable climate and jobs?

Breathable air is really nice. The plan is expected to annually prevent 1,100 hospitalizations, 220 heart attacks, and 3,500 early deaths. These added benefits are due to the fact that burning coal for electricity is a pretty dirty business, releasing not only carbon, but also volatile organic compounds (VOCs) and particulate matter.

7. What happens next?

No matter what happens on Tuesday, this case is likely to keep going. The 26 states that have filed against the CPP — along with Murray Energy, an Ohio-based coal company — have said they will take this case to the Supreme Court. The EPA will, as well, provided the next president does not direct the agency to scrap the rule altogether.